07色が数式でつながるバッジ型難易度選択

<main class="stage">
<div class="bhs is-demo" id="bhs" role="radiogroup" aria-label="難易度">
  <button type="button" class="bhs__badge" role="radio" aria-checked="false" data-i="0" tabindex="0">簡単</button>
  <button type="button" class="bhs__badge" role="radio" aria-checked="false" data-i="1" tabindex="-1">普通</button>
  <button type="button" class="bhs__badge" role="radio" aria-checked="true" data-i="2" tabindex="-1">難しい</button>
  <button type="button" class="bhs__badge" role="radio" aria-checked="false" data-i="3" tabindex="-1">とても難しい</button>
  <button type="button" class="bhs__badge" role="radio" aria-checked="false" data-i="4" tabindex="-1">最高</button>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 변수 3개
$duration: $dur-quick;
$easing: $ease-out;
$color: $subject-ink;

// 계산 겹: badgeHue(i) 가 배지 색을 (기준 색상각 + 번호*간격) 수식으로 구한다(JS) — scss 는 배지 모양만
@include stage($stage-orange);

.bhs { display: flex; flex-wrap: wrap; gap: $sp-2; justify-content: center; max-width: 290px; }
.bhs__badge {
  appearance: none; border: 2px solid transparent; border-radius: $r-pill;
  padding: $sp-2 $sp-3; font-weight: 700; font-size: 12px; color: $color; cursor: pointer;
  transition: transform $dur-quick $ease-pop, border-color $dur-quick $ease-out;
}
.bhs__badge:focus-visible { outline: 2px solid $subject-ink; outline-offset: 2px; }
.bhs__badge[aria-checked="true"] { border-color: $subject-ink; transform: scale(1.08); }

@media (max-width: 340px) {
  .bhs { max-width: 250px; }
  .bhs__badge { font-size: 11px; padding: $sp-1 $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  // 실사용 경로 적용: 실제로 배지를 골라도 확대·테두리는 트랜지션 없이 즉시 반영된다(색 자체는 JS 가 즉시 대입)
  .bhs__badge { transition: none; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.bhs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  justify-content: center;
  max-width: 290px;
}

.bhs__badge {
  appearance: none;
  border: 2px solid transparent;
  border-radius: 999px;
  padding: 8px 12px;
  font-weight: 700;
  font-size: 12px;
  color: #17141a;
  cursor: pointer;
  transition: transform 220ms cubic-bezier(0.2, 1.4, 0.4, 1), border-color 220ms ease-out;
}

.bhs__badge:focus-visible {
  outline: 2px solid #17141a;
  outline-offset: 2px;
}

.bhs__badge[aria-checked=true] {
  border-color: #17141a;
  transform: scale(1.08);
}

@media (max-width: 340px) {
  .bhs {
    max-width: 250px;
  }
  .bhs__badge {
    font-size: 11px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .bhs__badge {
    transition: none;
  }
}

(function () {
  var LEVELS = ['簡単', '普通', '難しい', 'とても難しい', '最高'];
  var BASE_HUE = 140, HUE_SPACING = 46, SAT = 45, LIGHT = 72;
  var root = document.getElementById('bhs');
  var badges = Array.prototype.slice.call(root.querySelectorAll('.bhs__badge'));
  var selected = 2;

  // 계산 겹: 배지 색을 고정 다섯 색이 아니라 단계 번호를 색상각 수식(기준 색상 + 번호*간격)에 넣어 구한다
  function badgeHue(i) { return (BASE_HUE + i * HUE_SPACING) % 360; }
  function badgeColor(i) { return 'hsl(' + badgeHue(i) + ', ' + SAT + '%, ' + LIGHT + '%)'; }
  function paint() {
    badges.forEach(function (b, i) {
      b.style.background = badgeColor(i);
      b.setAttribute('aria-checked', i === selected ? 'true' : 'false');
      b.setAttribute('tabindex', i === selected ? '0' : '-1');
    });
  }
  function human() { root.classList.remove('is-demo'); clearInterval(timer); }
  function select(i) { selected = i; paint(); }

  badges.forEach(function (b, i) {
    b.addEventListener('click', function () { human(); select(i); });
    b.addEventListener('keydown', function (e) {
      if (e.key === 'ArrowRight') { e.preventDefault(); human(); var n = Math.min(LEVELS.length - 1, selected + 1); select(n); badges[n].focus({ preventScroll: true }); }
      else if (e.key === 'ArrowLeft') { e.preventDefault(); human(); var p = Math.max(0, selected - 1); select(p); badges[p].focus({ preventScroll: true }); }
    });
  });

  var sequence = [4, 0, 3, 1, 2];
  var si = 0;
  function tick() { select(sequence[si % sequence.length]); si++; }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var timer = reduce ? null : setInterval(tick, 700);
  paint();
}());

import { useEffect, useRef } from 'react';
import styles from './DifficultySelectorBadgeHueShift.module.scss';

const LEVELS = ['쉬움', '보통', '어려움', '매우 어려움', '최고'];
const BASE_HUE = 140, HUE_SPACING = 46, SAT = 45, LIGHT = 72;
const SEQUENCE = [4, 0, 3, 1, 2];
const TICK_MS = 700;

export default function DifficultySelectorBadgeHueShift() {
  const rootRef = useRef<HTMLDivElement>(null);
  const badgeRefs = useRef<HTMLButtonElement[]>([]);

  useEffect(() => {
    const root = rootRef.current;
    if (!root || !badgeRefs.current) return undefined;
    const badges = badgeRefs.current;
    if (badges.length !== LEVELS.length) return undefined;

    let selected = 2;

    // 계산 겹: 배지 색을 고정 다섯 색이 아니라 단계 번호를 색상각 수식(기준 색상 + 번호*간격)에 넣어 구한다
    function badgeHue(i: number) { return (BASE_HUE + i * HUE_SPACING) % 360; }
    function badgeColor(i: number) { return 'hsl(' + badgeHue(i) + ', ' + SAT + '%, ' + LIGHT + '%)'; }
    function paint() {
      badges.forEach((b, i) => {
        b.style.background = badgeColor(i);
        b.setAttribute('aria-checked', i === selected ? 'true' : 'false');
        b.setAttribute('tabindex', i === selected ? '0' : '-1');
      });
    }
    let timer = 0;
    function human() { root!.classList.remove(styles['is-demo']); window.clearInterval(timer); }
    function select(i: number) { selected = i; paint(); }

    const offs = badges.map((b, i) => {
      function onClick() { human(); select(i); }
      function onKey(e: KeyboardEvent) {
        if (e.key === 'ArrowRight') { e.preventDefault(); human(); const n = Math.min(LEVELS.length - 1, selected + 1); select(n); badges[n].focus({ preventScroll: true }); }
        else if (e.key === 'ArrowLeft') { e.preventDefault(); human(); const p = Math.max(0, selected - 1); select(p); badges[p].focus({ preventScroll: true }); }
      }
      b.addEventListener('click', onClick);
      b.addEventListener('keydown', onKey);
      return () => { b.removeEventListener('click', onClick); b.removeEventListener('keydown', onKey); };
    });

    let si = 0;
    function tick() { select(SEQUENCE[si % SEQUENCE.length]); si++; }
    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    if (!reduce) timer = window.setInterval(tick, TICK_MS);
    paint();

    return () => { offs.forEach((off) => off()); window.clearInterval(timer); };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.bhs + ' ' + styles['is-demo']} ref={rootRef} role="radiogroup" aria-label="난이도">
        {LEVELS.map((label, i) => (
          <button
            key={label}
            type="button"
            className={styles.bhsBadge}
            ref={(el: HTMLButtonElement | null) => { if (el && badgeRefs.current) badgeRefs.current[i] = el; }}
            role="radio"
            aria-checked={i === 2 ? 'true' : 'false'}
            data-i={i}
            tabIndex={i === 0 ? 0 : -1}
          >
            {label}
          </button>
        ))}
      </div>
    </main>
  );
}